KR20010014414A - Cube corner sheeting mold and method of making the same - Google Patents

Abstract

The present invention relates to a thin plate suitable for use in a mold for forming a retroreflective cube edge element and a method for producing the same. Exemplary thin plates include cubic edge elements in a first row arranged in a first direction and cubic edge elements in a second row optionally arranged opposite. The machined surface of the sheet has a plurality of cube edge elements formed into optical surfaces defined by three sets of grooves. A set of opposing first and second grooves is formed in the machined surface of the sheet. The first set of grooves form a plurality of structures having first and second optical surfaces, the optical surfaces being disposed in mutually perpendicular planes intersecting along the reference edge. The second set of grooves forms a plurality of structures corresponding to opposite sides of the thin plate. The third groove is formed on the machined surface of the thin plate along an axis substantially perpendicular to the axes of the grooves of the first and second groove sets. The surface of the third groove intersects the plurality of structures in substantially mutually perpendicular planes to form a plurality of cube edge elements. By assembling a plurality of such thin plates, a mold useful for producing a retroreflective article such as a thin plate having a cube edge is formed.

Description

Sheet-molded mold having a cube edge and a method of manufacturing the same {CUBE CORNER SHEETING MOLD AND METHOD OF MAKING THE SAME}

Retroreflective materials are characterized by the ability to redirect light incident on the material back to the original light source. This property contributed to making the retroreflective sheet widely used in a variety of similar applications. Retroreflective laminate articles are widely used for flat and rigid articles such as road signs and barricades, but are also used for irregular or flexible surfaces. For example, the retroreflective thin plate may be attached to the side of a truck trailer, but in this case it is necessary to pass the thin plate past the pleats or overhanging rivets. The sheet can also be attached to flexible parts such as road vests' safety vests or other similar safety clothing. If the lower attachment surface is irregular or flexible, the retroreflective sheeting preferably has the ability to conform to the lower attachment surface without sacrificing the retroreflective property. In addition, the retroreflective sheeting needs to be flexible enough to be wound around the core, since the roll is often packaged or shipped in form.

Two types of retroreflective thin plates known are thin spherical thin plates and thin plates with cube edges. Microspheres, sometimes referred to as "bead-like" plates, are typically specular or diffuse reflecting materials (e.g. pigment particles, pieces of metal or vapor coats) in which the binder layer is at least partially embedded and retroreflects incident light. coat, etc.] are employed. Illustrative examples of this are disclosed in US Pat. Nos. 3,190,178 to McKenzie, 4,025,159 to McGrath, and 5,066,098 to Kult. It is advantageous that the microsphere-shaped sheets can be attached to wrinkled or flexible surfaces. In addition, due to the symmetrical geometry of the bead-type retroreflector, the microsphere-shaped thin plate exhibits a relatively uniform characteristic of total light return along the direction when rotated about an axis perpendicular to the surface of the thin plate. Thus, such microsphere-shaped thin plates are characterized by exhibiting relatively low sensitivity to the direction in which the thin plates are placed on a given surface. In general, however, such thin plates have a lower retroreflective efficiency compared to thin plates having cube edges.

A thin plate having a cube edge has a body region that typically has a substantially flat base surface and a structured surface having a plurality of cube elements opposite the base surface. Each cube edge element has three optical planes that are substantially perpendicular to each other, the three optical planes intersecting at a single reference point, ie a vertex. The base of the cube edge element acts as a hole through which light is transmitted into the cube edge element. In use, light incident on the base surface of the sheet is reflected off the base surface of the sheet, transmitted through the base of the cubic corner element disposed in the sheet, reflected from each of the three vertical cube corner optical surfaces, and then back toward the light source. do. The axis of symmetry of the cube edge element, also called the optical axis, is such an axis extending through the vertex of the cube edge and making the same angle as the three optical surfaces of the cube edge element. Cube edge elements typically exhibit the highest optical efficiency in response to light entering the base of the element along approximately the optical axis. The amount of light that is retroreflected by the retroreflector with cuboid edges is reduced as the angle of incidence is biased from the optical axis.

The maximum retroreflective efficiency of a retroreflective sheet having cuboid edges is a function of the geometry of the cube edge element on the sheet's structured surface. The terms 'active area' and 'effective hole' are used in the art to characterize the portion of the cube edge element that retroreflects light incident on the base of the cube edge element. Specific details relating to the determination of active holes in the cubic corner element configuration are beyond the scope of this specification. One method for determining the effective hole of the geometry of a cube edge is introduced in Eckhardt, July 1971, Applied Optics, Vol. 10, No. 7, pp. 1559-1566. U.S. Pat.No. 835,648 to Straubel also discusses the concept of effective holes. At a given angle of incidence, the active region may be determined by the geometric intersection of the projections of the image plane for third reflection in the same plane as the projections of the three cube edge faces in the plane perpendicular to the reflected incident light. The term 'active area ratio' is defined as the active area divided by the total area of the protrusions of the cube edge face. The retroreflective efficiency of the retroreflective sheet is directly correlated with the active area ratio of the cubic edge elements on the sheet.

In addition, the optical properties of the retroreflective pattern of the retroreflective sheeting are in part a function of the geometric shape of the cuboid edge element. Thus, if the geometric shape of the cube corner elements is distorted, corresponding distortions may occur in the optical properties of the thin plate. To prevent undesired physical deformation, the cubic edge elements of the retroreflective sheeting are typically made of a material having a sufficiently large modulus of elasticity such that the cube corner elements are not physically distorted while bending or elastically stretching the sheet. As mentioned above, it is often desirable for the retroreflective thin plate to be easily corrugated or to itself adhere the thin plate to a flexible substrate, or sufficiently flexible to roll the retroreflective thin plate to form a roll for storage and shipping.

The manufacture of retroreflective thin plates with cuboid edges begins with the fabrication of a master mold in which the desired geometry of the cubic edge element is molded in female or male form. The mold can be replicated by making a tool for forming a retroreflective sheet having cubic edges, using nickel electroplating, chemical vapor deposition, or physical vapor deposition. U. S. Patent No. 5,156, 863 to Pricon et al. Illustrates an overview process for forming a tool used for the production of retroreflective sheeting with cuboid edges. Known master mold fabrication methods include pin-bundling techniques, direct processing, and laminate techniques. Each of these methods has advantages and limitations.

In the case of the pin-bundle method, a plurality of pins having one end of a predetermined shape are bundled together to form a cubic edged retroreflective surface. Exemplary examples are presented in US Pat. Nos. 1,591,572 to Stimson, 3,926,402 to Henan, 3,541,606 to Henan et al., 3,632,695 to Howell. The pin-bundle method provides the ability to fabricate various cube edge shapes in a single mold. However, the pin-bundling method is not economically and technically practical in the production of small cube edge elements (eg, less than about 1.0 mm).

In the case of direct processing, a series of grooves are formed in a single substrate to form a retroreflective surface having cube edges. Illustrative examples of this are provided in US Pat. Nos. 3,712,706 to Stamm and 4,588,258 to Hoopman. Direct machining provides the ability to precisely machine very small cube edge elements that are compatible with flexible retroreflective sheeting. However, it is not practically possible to use a direct machining method to produce a constant cube edge shape with very high effective holes at low entrance angles. By way of example, the theoretical maximum total light return of the cube edge element shape described in US Pat. No. 3,712,706 is about 67%.

In the case of the lamination method, a plurality of laminates having one end of a predetermined shape are assembled to form a retroreflective surface having a cube edge. In the case of molded reflectors disclosed in German Patent Publication (OS) 19 17 292, International Publication No. WO 94/18581 (Bohn et al.), WO 97/04939 (Mimura et al.), WO 97/04940 (Mimura et al.), Grooves are formed on a plurality of plates. In this case, the plates are tilted at an angle and each second plate is moved crosswise. As a result of this process, a plurality of such cube corner elements are obtained in which two machining surfaces are formed on the first plate and one side is formed on the second plate, respectively. DE 42 36 799, issued to Gubela, discloses a method of making a molding tool having a cube surface for producing cube edges. The inclined surface is ground or cut in the first direction over the entire length of one edge of the band. Then, a plurality of notches are formed in the second direction to form a band-shaped cube edge reflector. Finally, a plurality of notches are formed perpendicular to the side of the band. A related patent is German Patent Publication No. 44 10 994 C2 (Gubela). The reflector disclosed in this patent is characterized by a reflective surface of concave curvature.

The present invention relates generally to a mold suitable for use in forming a retroreflective sheet having a cuboid edge and a method of manufacturing the same. Specifically, the present invention relates to a mold molded from a plurality of thin layered bodies and a manufacturing method thereof.

1 is a perspective view of a single sheet of steel suitable for use in the disclosed method.

2 is an end view of a single sheet of steel that has undergone a first machining step.

3 is a side view of a single sheet of steel having undergone a first machining step.

4 is a plan view of a single sheet of steel that has undergone a first machining step.

5 is an end view of a single sheet of steel that has undergone a second machining step.

6 is a side view of a single sheet of steel undergoing a second machining step.

7 is a plan view of a single sheet of steel that has undergone a second machining step.

8 is a perspective view of a single sheet of steel that has undergone a second machining step.

9 is an end view of a single sheet of steel that has undergone a third machining step.

10 is a side view of a single sheet of steel that has undergone a third machining step.

11 is a plan view of a single sheet of steel that has undergone a third machining step.

12 is a perspective view of a single sheet metal having undergone a third machining step.

Figure 13 is a plan view of another embodiment of a single sheet of steel that has undergone a third machining step.

14 is an end view of another embodiment of a single sheet of steel that has undergone a third machining step.

15 is a side view of another embodiment of a single sheet of steel that has undergone a third machining step.

16 is a perspective view of a plurality of thin plates.

17 is an end view of a plurality of thin plates oriented in the first direction.

18 is an end view of a plurality of thin sheets subjected to a first machining operation.

19 is a side view of a plurality of thin sheets subjected to a first machining operation.

20 is an end view of a plurality of thin plates oriented in a second direction.

21 is an end view of a plurality of thin sheets that have undergone a second machining operation.

22 is a side view of a plurality of thin sheets subjected to a second machining operation.

23 is an end view of a plurality of thin sheets subjected to a third machining operation.

24 is a plan view of a plurality of thin sheets subjected to a third machining operation.

25 is a plan view showing a part of the processed surface of a single thin plate;

FIG. 26 is a side elevation view of the machining surface shown in FIG. 25.

FIG. 27 is a side elevation view of the machining surface shown in FIG. 25.

The present invention relates to a master mold suitable for use in forming a retroreflective thin plate from a plurality of layered bodies and a method of manufacturing the mold. Master molds made in accordance with the methods disclosed herein enable the production of thin plates having retroreflective cube edges exhibiting levels of retroreflective efficiency close to 100%. In order to facilitate the manufacture of flexible retroreflective thin plates, the disclosed method enables the production of retroreflective elements having cube edges whose width is 0.010 mm or less. In addition, the present invention enables the production of retroreflective sheets having cuboid edges exhibiting symmetrical retroreflective capabilities in at least two different directions.

Also disclosed is a method for efficiently and cost-effectively manufacturing a mold formed of a plurality of layered bodies. In particular, according to the disclosed method, by reducing the number of layered bodies required to form a cube edge element in a predetermined density in sheet metal, it saves time and costs associated with the manufacture of such a mold.

In one embodiment, a thin plate suitable for use in a mold for forming a retroreflective article having a cuboid edge has an opposite first major surface and a second major surface defining a first reference plane therebetween, And further comprising a machining surface connecting between the first major surface and the second major surface, the machining surface being substantially parallel to and perpendicular to the first reference plane, and the first reference plane. And a third reference plane perpendicular to the second reference plane. The thin plate comprises: (a) a first groove set comprising at least two parallelly adjacent V-shaped grooves having a first groove surface and a second groove surface that are substantially orthogonal to form a first reference edge on the machined surface of the thin plate; And (b) a second set of grooves comprising at least two parallelly adjacent V-shaped grooves having a third groove surface and a fourth groove surface that are substantially orthogonal to a processing surface of the thin plate to form a second reference edge; And (c) having a fifth groove surface and a sixth groove surface on the processed surface of the thin plate, the fifth groove surface being substantially orthogonal to the first groove surface and the second groove surface, disposed in the first direction. One or more first cube edges formed, wherein the sixth groove surface is disposed in a second direction different from the first direction so as to be substantially orthogonal to the third groove surface and the fourth groove surface. 2 containing at least one such groove forming a corner of a cube It includes such a third groove set.

In one embodiment, the first and second sets of grooves are formed such that their respective reference edges extend along an axis perpendicular to the first reference plane in plan view. The third set of grooves includes a single groove having a vertex extending along an axis included by the third reference plane. In this embodiment, the sheet comprises a first row of cubical edge elements defined by a groove and a third groove of the first set of grooves, and a second row of cube edge elements defined by a groove and a third groove of the second groove set. do.

The three mutually orthogonal optical surfaces of each cube edge element are preferably formed of a single thin plate. All three optical surfaces are preferably formed by a machining process to ensure the surface of the optical quality. In order to minimize alignment problems and damage due to the handling of the sheet, it is desirable to maintain a flat interface between the adjacent first and second major surfaces during the machining and subsequent processes.

The present invention also discloses a method for producing a thin plate suitable for use in a mold for forming a retroreflective article having a cubic edge, in which the thin plate opposes a first major surface forming a first reference plane therebetween. And a second major surface, and also having a machining surface connecting between the first major surface and the second major surface, the machining surface being substantially parallel thereto and perpendicular to the first reference plane. A second reference plane that is, and a third reference plane that is perpendicular to the first and second reference planes are defined. The method comprises: (a) processing a first set of grooves comprising at least two firstly parallel V-shaped grooves having a first groove surface and a second groove surface that are substantially orthogonal to form a first reference edge; Forming a second groove set comprising (b) at least two second groove sets comprising at least two parallel adjacent V-shaped grooves having a third groove surface and a fourth groove surface that are substantially orthogonal to form a second reference edge; Forming on the processed surface of the substrate; And (c) at least one first cube edge having a fifth groove surface and a sixth groove surface, wherein the fifth groove surface is disposed in a first direction substantially perpendicular to the first groove surface and the second groove surface. And the sixth groove surface has one or more second cube edges disposed in a second direction different from the first direction so as to be substantially orthogonal to the third groove surface and the fourth groove surface. Forming a third set of grooves on the processed surface of the sheet;

The present invention also relates to a mold assembly having a plurality of thin plates, wherein the thin plates have opposing parallel first and second major surfaces defining a first reference plane therebetween. And further comprising a machining surface connecting between the first major surface and the second major surface, the machining surface being substantially parallel to and perpendicular to the first reference plane, and the first reference plane. And a third reference plane perpendicular to the second reference plane. The processing surfaces of the plurality of thin plates comprise (a) parallel adjacent adjacent V-shaped grooves having a first groove surface and a second groove surface that are substantially orthogonal to the processing surfaces of each thin plate to form a first reference edge in each thin plate. A first set of grooves comprising two or more, and (b) a parallel adjacent V having a fourth groove surface and a third groove surface that is substantially orthogonal to the machined surface of each thin plate to form a second reference edge in each thin plate. A second set of grooves including two or more male grooves, and (c) a fifth groove surface and a sixth groove surface on the machined surfaces of the plurality of thin plates, the fifth groove surface having the first groove surface and Form at least one first cube edge disposed in a first direction substantially perpendicular to a second groove surface, wherein the sixth groove surface is substantially orthogonal to the third groove surface and the fourth groove surface; At least one second mouth disposed in a second direction different from the direction It includes such a third groove set including such a groove forming the at least one body edge.

In one embodiment of such a mold assembly, the first set of grooves extends substantially throughout each first major surface of the plurality of thin plates, and the second set of grooves is substantially each second of the plurality of thin plates. It extends across the major surface. Further, the first groove set and the second groove set are formed to extend along an axis perpendicular to each first reference plane when the respective reference edges are viewed in plan view. Finally, the third set of grooves includes only one groove in each sheet having vertices extending along an axis parallel to the third reference plane of each sheet. According to this embodiment, each thin plate has a cubic cornered element in a first row defined by the grooves of the first and third groove sets, and a second defined by the grooves of the second and third groove sets. Rows of cuboid edge elements are included.

Another disclosed herein relates to a method of manufacturing a plurality of sheets of thin sheet suitable for use in a mold for forming a retroreflective article having a cubic edge, each sheet having an opposing first major surface defining a first reference plane therebetween. In addition to having a second major surface, there is also a machining surface connecting between the first major surface and the second major surface, the machining surface being substantially parallel thereto and perpendicular to the first reference plane. A method of manufacturing a plurality of such thin plates defining a second reference plane and a third reference plane perpendicular to the first reference plane and the second reference plane. The method comprises the steps of (a) orienting a plurality of thin plates such that their respective first reference planes take a first angle with respect to the reference axis that is parallel to each other and to a fixed reference axis; (C) forming a first set of grooves on the machined surface of each thin plate, the first groove set comprising two or more parallelly adjacent V-shaped grooves having a first groove surface and a second groove surface forming a first reference edge; Directing the thin plates of so that their respective first reference planes are parallel to each other and disposed at a second angle with respect to the fixed reference axis; and (d) forming substantially second orthogonal second reference edges on each individual thin plate. Forming a second set of grooves on the machined surface of each thin plate, the second set of grooves comprising two or more parallelly contiguous V-shaped grooves having a third groove surface and a fourth groove surface; Going groove surface And the fifth groove surface forms at least one first cube edge disposed in a first direction substantially perpendicular to the first groove surface and the second groove surface, and the sixth groove surface is the third groove. A plurality of third set of grooves comprising at least one such groove substantially perpendicular to the surface and the fourth groove surface to form at least one second cube edge disposed in a second direction different from the first direction; Forming on the processed surface of the two thin plates.

In the disclosed method, the plurality of thin plates is assembled in a suitable fixture forming a base surface. The fastener has a first reference plane substantially parallel, and between about 1 ° and about 85 °, more preferably between about 10 ° and about 60 °, relative to a fixed reference axis that is normal to the base plane. The thin plate is fixed to be arranged at an angle. The first set of grooves is then formed by removing a portion of each thin plate adjacent to the machined surface of the plurality of thin plates using, for example, suitable material removal techniques such as ruling, ply cutting, grinding or milling. The plurality of thin plates is then reassembled in the fixture and the first reference plane is substantially parallel and is about 1 ° to about 85 ° with respect to a fixed reference axis that is normal to the base plane, more preferably. Preferably, the sheet is secured to be placed at a second angle between about 10 degrees and about 60 degrees. Next, the second groove set is formed by using a suitable material removal technique as described above. Next, the plurality of thin plates are reassembled by a fastener, and the thin plates are fixed such that the second reference plane is substantially parallel to the reference axis. The third set of grooves is then formed using the appropriate material removal technique described above. The third groove set preferably forms one groove in each thin plate.

In describing the various embodiments below, special terminology is used for the sake of clarity. However, it is to be understood that such terminology is not intended to be in a limiting sense, and that each term selected includes all technical equivalents that function similarly. Related applications filed on the same day as the present specification include 'Retroreflective Cube Corner Sheeting Mold and Sheeting Formed Therefrom' (Atty.Docket No.53305USA5A). ',' Retroreflective Cube Corner Sheeting, Molds Therefore, and Methods of Making the Same (Atty.Docket No.53318USA8A) ',' Highly Inclined Cube Corner Elements Tiled Retroreflective Sheeting Composed of Highly Canted Cube Corner Elements (Atty.Docket No.53285USA9A), 'Retroreflective Cube Corner Sheeting Mold and Method of Making the Same) (Atty.Docket No.51952USA6A) and 'Dual Orientation Retroreflective Sheeting (Atty.Docket No.52303USA8B)' The.

In the disclosed embodiments, full cuboid edge elements of various sizes and shapes may be used. The base edges of aligned and adjacent complete cuboid corner elements are not all co-planar. In contrast, the base edges of aligned and adjacent truncated cube edge elements are usually on the same plane. A complete cuboid corner element has a greater total light return than a truncated cubic corner element for a given degree of inclination, but at larger angles of incidence the total return light is lost more quickly. One advantage of a perfect cuboid edge element is that the total return light is greater at small angles of incidence without largely losing its performance at larger angles of incidence.

The expected total light return (TLR) for the combined cubic edge pair arrays can be calculated from the active area ratio and the ray intensity. The brightness can be reduced by reflection from each of the three cube edge surfaces and the loss of the anterior surface for retroreflected light rays. Total return light is defined as the product of the active area ratio and the luminosity or the proportion of light that is retroreflected out of the total incident light. Details regarding total return light for a directly machined cuboid edge arrangement are disclosed in Stamm, US Pat. No. 3,712,706.

An embodiment of a thin plate and a method of manufacturing the same will be described with reference to FIGS. 1 to 12. 1 and 2 show representative thin plates 10 useful for the manufacture of molds suitable for forming retroreflective thin plates. The thin plate 10 has a first major surface 12 and an opposite second major surface 14. The thin plate 10 also has a working surface 16, and a bottom surface 18 extending from the opposite side between the first major surface 12 and the second major surface 14. The thin plate 10 also has a first end face 20 and a second end face 22 opposite thereto. In a preferred embodiment, the thin plate 10 is a rectangular polyhedron whose surfaces opposite each other are substantially parallel. However, it can be seen that the surfaces of the thin plate 10 need not be parallel.

For the purpose of explanation, the thin plate 10 is characterized by superimposing a Cartesian coordinate system on its structure in three-dimensional space. The first reference plane 24 is in the middle between the first major surface 12 and the second major surface 14. The first reference plane 24, also called the x-z plane, has a y-axis as its normal vector. The second reference plane 26, also called the x-y plane, extends substantially on the same plane as the machining surface 16 of the thin plate 10 and has a z axis as its normal vector. A third reference plane 28, also referred to as the y-z plane, is centered between the first end face 20 and the second end face 22, and has an x axis as its normal vector. For clarity, various geometrical attributes of this embodiment are described herein with reference to the Cartesian reference plane. However, it will be appreciated that such geometry properties may be described with reference to other coordinate systems or sheet structures.

2 to 12 illustrate the formation of a structured surface comprising a plurality of cubic edged elements optically opposite at the machining surface 16 of the thin plate 10. In brief, in accordance with a preferred embodiment, a first set of grooves comprising at least two parallel and adjacent grooves 30a, 30b, 30c, etc. (collectively denoted as 30) is provided with a machined surface ( 16) (FIGS. 2 to 4). A second set of grooves comprising at least two parallel and adjacent grooves 38a, 38b, 38c and the like (collectively denoted by 38) is formed on the machined surface 16 of the thin plate 10 (FIGS. 5 to FIG. 5). 7). The first set of grooves and the second set of grooves are generally along a first reference plane 24 to form a structured surface comprising a plurality of alternating peaks and a V-shaped valley (FIG. 8). It is good to cross. The first and second groove sets 30, 38 need not be aligned as shown in FIG. Alternatively, the peak and V-shaped valleys may be offset relative to one another, as shown in FIG. 13.

Next, a third groove 46 is formed in the processing surface 16 of the thin plate 10 (FIGS. 9 to 11). The third groove 46 preferably extends along an axis substantially perpendicular to the direction in which the first groove and the second groove are formed. Formation of the third groove 46 results in a structured surface comprising a plurality of cuboid edge elements with optical surfaces perpendicular to each other in the thin plate (FIG. 12). The term "groove set" as used herein refers to all parallel grooves formed in the machining surface 16 of the thin plate 10.

Hereinafter, the embodiments will be described in more detail. 2 to 4, a first set of grooves comprising at least two parallel and adjacent grooves 30a, 30b, 30c, etc. (collectively denoted by reference numeral 30) is a machined surface of the thin plate 10. 16). The groove is a first groove surface 32a, 32b, 32c, etc. (collectively indicated by reference numeral 32) and intersecting at the vertices 33b, 33c, 33d, etc. (collectively indicated by reference numeral 33) of the groove. 2 groove surfaces 34b, 34c, 34d and the like (collectively indicated by reference numeral 34) are formed. A single groove surface 32a may be formed at the edge of the thin plate by the groove forming operation. Groove surfaces 32a, 34b of adjacent grooves intersect at right angles along reference edge 36a. As used herein, the term 'substantially right angle' or 'approximately right angle' means that the dihedral angle between each surface is about 90 °, which is described in Appledon US Patent No. 4,775,219. It is also conceivable to slightly vary the degree of right angle as disclosed and claimed in the call. Similarly, adjacent groove surfaces 32b and 34c intersect at right angles along the first reference edge 36b. This pattern is preferably repeated throughout the processing surface 16 of the thin plate 10 as shown in FIGS. 3 and 4. The vertices 33 of each groove are preferably separated by a distance between about 0.01 mm and about 1.0 mm.

In the embodiment of FIG. 2, the grooves such that the vertices 33 and the first reference edge 36 of each groove extend along an axis intersecting the first major surface 12 of the thin plate 10 and the machining surface 16. 30 is formed. In this embodiment, the machining surface 16 of the thin plate 10 includes portions that remain unchanged by forming a plurality of grooves 30. By forming grooves deeper into the machining surface 16, the vertices 33 and the first reference edge 36 of each groove are formed in the first major surface 12 and the second major surface 14 of the thin plate 10. It can be appreciated that the grooves may be formed to extend along an axis that intersects with. In addition, in the embodiment of FIGS. 2-4, the first reference plane 24 and the second reference plane 26 at right angles such that the reference edge 36 appears perpendicular to the reference plane 24 in the plan view of FIG. 4. The groove 30 is formed such that each of the first reference edges 36 is disposed in a plane intersecting with each other.

2-4, the grooves 30 are formed such that all of the first reference edges 36 are disposed on a common plane intersecting the second reference plane 26 at an acute angle θ ₁ of about 27.8 °. It is. Alternatively, the groove 30 may be formed such that the reference edge 36 intersects the reference plane 26 at an angle other than 27.8 °. In general, it is also possible for each reference edge 36 to be grooved to intersect the reference plane 26 at any angle between about 1 ° and about 85 °, more preferably between about 10 ° and about 60 °. Do.

5 to 8, a second set of grooves comprising at least two parallel and adjacent grooves 38a, 38b, 38c, etc. (collectively denoted by reference numeral 38) is provided with a machined surface ( 16). The grooves 38 are, as shown, third groove surfaces 40a, 40b, 40c, etc. intersecting at the vertices 41b, 41c, 41d, etc. (collectively indicated by reference numeral 41) of the grooves (collectively the drawings). And the fourth groove surface 42b, 42c, 42d, etc. (collectively indicated by reference numeral 42) are formed. At the edge of the thin plate, a single groove surface 40a may be formed by the groove forming operation. Groove surfaces 40a and 42b of adjacent grooves intersect at substantially right angles along reference edge 44a, which, for the purposes of the present disclosure, has a backside angle between groove surfaces 40a and 42b of about 90 degrees. Means °. Similarly, adjacent groove surfaces 40b and 42c intersect at right angles along the second reference edge 44b. This pattern is preferably repeated throughout the machining surface 16 of the thin plate 10. The apex portions 41 of the grooves may be spaced apart from each other by about 0.01 mm to 0.10 mm.

Referring to FIG. 5, it can be seen that the groove 38 is formed such that the reference edge 44 extends along an axis that intersects the machining surface 16 and the second major surface 14 of the thin plate 10. In this embodiment, the reference edge 44 (and the vertex 41 of the groove) intersects the second reference plane 26 of the thin plate 10 at an acute angle θ ₂ of about 27.8 °. As noted above, grooves may be formed that intersect the reference plane 26 at any angle between about 1 ° and 85 °.

In the embodiment of FIGS. 5-8, the first reference plane 24 and the second reference plane 26 at right angles such that the reference edge 44 appears perpendicular to the first reference plane 24 in the top view of FIG. 7. The groove 38 is formed such that each of the reference edges 44 is disposed in a plane intersecting with the cross-section. 7, in particular, the apex 41 of the groove is substantially coplanar with the apex 33 of the groove, and the reference edge 44 is substantially coplanar with the reference edge 36. It is preferable to form the groove 38 to be at. Alternatively, the vertices 33 and 41 of the groove and the reference edges 36 and 44 can be moved relative to each other. In other embodiments, the depths of the vertices 33, 41 of the grooves may vary with respect to each other.

8 is a perspective view of a representative thin plate 10 that has completed the shaping of the groove 38. The thin plate 10 includes a series of grooves 30, 38 formed in the processing surface 16 as described above. The reference edges 36, 44 intersect approximately along the first reference plane 24, forming a plurality of peaks. Similarly, the vertices 33, 41 of the grooves intersect approximately along the first reference plane, forming a plurality of valleys between the peaks.

9 to 12 show an embodiment of the thin plate 10 following the formation of the third groove 46 of the thin plate 10. In this embodiment, the third groove 46 intersects the fifth groove surface 48 and the sixth groove surface 50 at the apex 52 of the groove along the axis encompassed by the first reference plane 24. ). It is important to form the third groove 46 such that the fifth groove surface 48 is disposed in a plane substantially perpendicular to the first groove surface 32 and the second groove surface 34. This causes the fifth groove surface 48 to form an angle equal to the angle θ ₁ with respect to the first reference plane 24, preferably the sixth groove surface likewise with respect to the first reference plane 24. It can be achieved by forming a third groove 46 to form the same angle _{(θ 2) (θ 1,} θ 2 is equal to the θ _1, θ ₂ in FIG. 5). By forming the fifth groove surface 48, a plurality of cuboid edge elements 60a, 60b, etc. (collectively indicated by reference numeral 60) are formed on the machined surface 16 of the thin plate 10. Each cube edge element 60 is a portion of the first groove surface 32, the second groove surface 34, and the fifth groove surface 48 that intersect at a point forming a cube edge peak or vertex 62. Determined by Similarly, the sixth groove surface 50 is disposed in a plane substantially perpendicular to the third groove surface 40 and the fourth groove surface 42 intersecting with each other at the point forming the cube edge peak or vertex 72. do. Similarly, by forming the sixth groove surface 50, a plurality of cuboid edge elements 70a, 70b, etc. (collectively indicated by reference numeral 70) are formed on the processed surface 16 of the thin plate 10. Each cube edge element 70 is defined by a portion of the third groove surface 40, the fourth groove surface 42, and the sixth groove surface 50. It is preferable that both the fifth groove surface 48 and the sixth groove surface 50 form a plurality of cube edge elements on the machining surface 16 of the thin plate 10. However, it can be appreciated that only the fifth groove surface 48 or the sixth groove surface 50 may form the third groove 36 to form a cubic edged element.

Various features of the thin plate 10 will be described with reference to FIGS. 11 and 12. In the disclosed embodiment, the back angle defined by the opposing surfaces of the grooves 30, 38 is 90 °. The first reference edge 36 and the second reference edge 44 are disposed in a plane crossing the first reference plane 24 and the second reference plane 26 at right angles. Thus, in the top view of FIG. 11, the reference edges 36, 44 extend along an axis substantially perpendicular to the first reference plane 24. Reference edge 36 extends along an axis that intersects first major surface 12 of sheet 10 and intersects second reference plane 26 at an acute angle of about 27.8 °. The reference edge 44 also extends along an axis that intersects the second major surface 14 of the thin plate 10 and intersects the second reference plane 26 at an acute angle of about 27.8 °. The vertex of the third groove 46 extends along an axis substantially parallel to the first reference plane 24, and the backside angle between the fifth groove surface 48 and the sixth groove surface 50 is about 55.6 °. .

The machining surface 16 is preferably formed using techniques such as ruling, milling, grooving, fly-cutting and precision machining. In one embodiment, the second major surface 14 of the thin plate 10 can be substantially matched to a substantially flat surface, such as the surface of a precision machining tool, and has a V-shaped cutting tool with an included angle of 90 °. Is moved along an axis that intersects the first machining surface 12 and the second reference plane 26 at an angle θ ₁ of 27.8 °, thereby moving each groove 30a, 30b, etc. of the first article groove to the machining surface ( 16) can be formed. In the disclosed embodiment, each groove 30 is formed to the same depth at the machining surface, and the cutting tool is laterally moved by the same distance between adjacent grooves with substantially the same grooves. Next, the first major surface 12 of the thin plate 10 may be matched with the flat surface, and the V-shaped cutting tool having an angle of 90 ° may be connected with the second machining surface 14 and the second reference plane 26. By moving along the axis intersecting at an angle θ ₂ of 27.8 °, each groove 38a, 38b, or the like can be formed in the machining surface 16. Finally, the bottom surface 18 of the thin plate 10 may be mated to a flat surface, and a V-shaped cutting tool having a 55.6 ° angle of inclination is substantially parallel to the base surface 18 and in the first reference plane 24. By moving along the axis included therein, the third groove 46 can be formed in the machining surface 16. Although the three groove forming steps were repeated in a specific order, those skilled in the art will appreciate that the order of the steps is not important. That is, the groove forming step may be performed in any order. In addition, those skilled in the art will appreciate that three sets of grooves may be formed in the matched sheet at one location, and the present application contemplates this method. In addition, the particular mechanism for physically, chemically or electromagnetically fixing the sheet is not critical.

In order to form a mold suitable for use in shaping the retroreflective article, a plurality of thin plates 10 having a processing surface 16 comprising the cuboid edge elements 60 and 70 formed as described above may be fitted with a suitable fixture. Can be assembled together. Next, by replicating the processing surface 16 using, for example, a precision replication technique such as nickel electroplating, a negative copy of the processing surface 16 is formed. Electroplating techniques are those known to those skilled in the art of retroreflective technology (see, eg, US Pat. Nos. 4,478,769 and 5,156,863 to Pricon et al.). The positive replica replica of the machining surface 16 can then be used as a mold to form a retroreflective article having a positive copy of the machining surface 16. More generally, future generations of electrically formed replicas are molded and assembled together to form larger molds. The positive replica of the processing surface 16 or the processing surface of the thin plate 10 may also be used as an embossing tool for forming a retroreflective article (see Japanese 8-309851 and US Pat. No. 4,601,861 to Pricon). . Those skilled in the art will appreciate that the machined surface 16 of each thin plate 10 functions independently as a retroreflective body. Thus, it is not necessary to place adjacent thin plates in the mold at precise angles or distances from each other.

16-24 provide another method of forming a plurality of thin plates suitable for use in a mold suitable for forming retroreflective water pools. In the embodiment of FIGS. 16 to 24, a plurality of cuboid edge elements are formed on the machined surface of the plurality of thin plates, and the thin plates are held together in an assembled state rather than being kept separate as described above. The plurality of thin plates 10 may be assembled such that the machining surface 16 is substantially coplanar. In brief, the thin plates 10 are oriented such that their respective first reference planes are arranged at a first angle β ₁ with respect to the reference axis 82 (FIG. 17) to which it is fixed. A first set of grooves including at least two V-shaped grooves are formed in the processing surface 16 of the plurality of thin plates 10 (FIGS. 18 and 19). The thin plates are then oriented such that their respective first reference planes are arranged at a second angle β ₂ with respect to the reference axis 82 (FIG. 20). A second set of grooves including at least two V-shaped grooves are formed in the processing surface 16 of the plurality of thin plates 10 (FIGS. 21 and 22). A third set of grooves, which preferably include at least one V-shaped groove, is also formed on the processing surface 16 of each thin plate 10 (FIG. 23). By forming a third set of grooves, a structured surface is formed that includes a plurality of cuboid edge-like elements on the machined surface of the plurality of thin plates 10 (FIG. 24).

16 to 24 will be described in more detail. In FIG. 16, a plurality of thin plates 10 are assembled together such that the first major surface 12 of one thin plate 10 is adjacent to the second major surface 14 of the adjacent thin plate 10. The thin plate 10 may be assembled in a conventional fixture capable of fixing a plurality of adjacent thin plates. The details of the fixture are not important. However, the fixture defines a base surface 80 which is preferably substantially parallel to the bottom surface 18 of the thin plate 10 when the thin plate 10 is positioned as shown in FIG. 16. The plurality of thin plates 10 is characterized by a Cartesian coordinate system as described above. The processing surface 16 of the plurality of thin plates 10 is preferably substantially coplanar when the thin plates are placed with the first reference plane 24 perpendicular to the base surface 80.

In FIG. 17, the thin plate 10 is oriented such that its first reference plane 24 is disposed at a first angle β ₁ from a fixed reference axis 82 perpendicular to the base surface 80. In one embodiment, the first angle β ₁ is about 27.8 °. However, the first angle β ₁ may alternatively be in a range between about 1 ° and about 85 °, more preferably between about 10 ° and about 60 °.

18 and 19, the first set of grooves including a plurality of parallelly adjacent V-shaped grooves (30a, 30b, 30c, etc.) (collectively indicated by reference numeral 30) is a thin plate is the angle (β ₁ ) Is formed on the machining surface 16 of the plurality of thin plates 10. At least two adjacent grooves 30 are formed in the machining surface 16 of the plurality of thin plates 10. The groove 30 is a first groove surface 32a, 32b, 32c, etc. (collectively referred to) intersecting at the vertices 33b, 33c, 33d, etc. (collectively indicated by reference numeral 33) of the groove, as shown. 32) and second groove surfaces 34b, 34c, 34d, etc. (collectively indicated by reference numeral 34) are determined. A single groove surface 32a may be formed at the edge of the thin plate by the forming operation of the groove. Groove surfaces 32a and 34b of adjacent grooves intersect at approximately right angles along reference edge 36a. Similarly, adjacent groove surfaces 32b and 34c intersect at right angles along the reference edge 36b. This pattern is preferably repeated throughout the machining surface 16 of the thin plate 10.

By removing a portion of the machining surface 16 of the plurality of thin sheets using various material removal techniques including precision machining techniques such as milling, ruling, grooving and fly cutting, chemical etching or laser stripping techniques, etc. 30). In one embodiment, the groove 30 transversely crosses the machining surface 16 of the plurality of thin plates 10 along an axis substantially parallel to the base surface 80 with a diamond cutting tool having an angle of 90 °. It is formed in high precision machining operations. Alternatively, the diamond cutting tool may move along an axis that is not parallel to the base surface 80 such that the tool cuts to varying depths across the plurality of thin plates 10. It will be appreciated that the machining tool may remain stationary while the plurality of thin plates are placed in motion, and the relative motion between the thin plate 10 and the machining tool may also be considered.

In the embodiment of FIGS. 18 and 19, the groove 30 is formed to a depth such that each first reference edge 36 intersects the first major surface 12 and the second major surface 14 of the sheet. . Thus, in the end view of FIG. 18, the reference edge 36 and the apex 33 of the groove form a substantially continuous line extending along an axis parallel to the base surface 80. In addition, the groove 30 is formed such that the reference edge 36 is disposed in a plane crossing at right angles with each of the first reference plane 24 and the second reference plane 26. Thus, in a plan view similar to FIG. 4, the first reference edge 36 appears perpendicular to each first reference plane 24. However, the grooves 30 may be formed at smaller depths or along other axes, as shown in FIGS.

In FIG. 20, the thin plates 10 are each oriented such that their first reference planes 24 lie at a second angle β ₂ from a fixed reference axis 82 in the vertical direction of the base surface 80. In one embodiment, the second angle β ₂ is approximately 27.8 °. However, the second angle β ₂ may optionally vary between about 1 ° and about 85 °, preferably between about 10 ° and about 60 °. Angle (β ₂₎ and is independent of the angle (β _1), need not be the same as the angle (β _1). In order to orient the plurality of thin plates 10 at an angle β ₂ , the thin plates 10 are preferably separated from the fixture and reassembled so that their first reference planes are each placed at an angle β ₂ .

21 and 22, a thin plate 10 in which a second set of grooves comprising a plurality of adjacent parallel V-grooves 38b, 38c, etc. (collectively denoted by reference numeral 38) lies at an angle β ₂ . Is formed on the machining surface 16. Two or more adjacent grooves 38 are formed in the machining surface 16 of the plurality of thin plates 10. The groove 38 is referred to as a third groove surface 40a, 40b, 40c, etc. (collectively 40) intersecting at the apex portions 41b, 41c, 41d, etc. (collectively denoted by 41) of the groove as shown. Display] and fourth groove surfaces 42b, 42c, 42d and the like (collectively indicated by reference numeral 42). The grooves formed at the edges of the thin plate may form only a single groove surface 40a. Importantly, the third groove surface 40a and the fourth groove surface 42b of the adjacent grooves intersect at right angles along the reference edge 44a. Similarly, third groove surface 40b and fourth groove surface 42c also intersect at right angles along reference edge 44b. This pattern is preferably repeated across the entire processing surface 16 of the plurality of thin plates 10.

The groove 38 is also preferably formed by a high precision machining operation, in which a diamond cutting tool with a 90 ° angle is formed by a plurality of thin plates along a cutting axis substantially parallel to the base surface 80. It is repeatedly moved across the machining surface 16 of 10). It is important that the surfaces of adjacent grooves 38 intersect along the reference edge 44 to form a right backside angle. The angle of measurement of each groove measured may be an angle other than 90 ° as described in connection with FIG. 15. The groove 38 is preferably formed in the processing surface 16 of the plurality of thin plates 10 to the same depth as the groove 30 of the first groove set. Further, the groove 38 is preferably formed such that its vertex 41 is substantially coplanar with the groove vertex 33 and the reference edge 44 is substantially coplanar with the reference edge 36. . After the formation of these grooves 38, each thin plate 10 preferably has a shape as shown in FIG.

In FIGS. 23 and 24, a third set of grooves, preferably including one or more grooves 46 of each thin plate 10, are formed on the machined surface 16 of the plurality of thin plates 10. In the disclosed embodiment, the third grooves 46a, 46b, 46c, etc. (collectively denoted by reference numeral 46) are groove vertices 52a, 52b, 52c, etc., along an axis parallel to the respective first reference plane 24. ) Fifth groove surfaces (48a, 48b, 48c, etc.) intersecting at [typically denoted by reference numeral 52] (collectively denoted by reference numeral 48) and sixth groove surfaces (50a, 50b, 50c, etc.) (collectively 50 Mark]. Importantly, each fifth groove surface 48 is formed to lie in a plane substantially perpendicular to each first groove surface 32 and each second groove surface 34. In the formation of the fifth groove surface 48, a plurality of cuboid edge elements 60a, 60b, etc. (collectively denoted by reference numeral 60) are produced on the machined surface 16 of each thin plate 10.

Each cube edge element 60 is a portion of the first groove surface 32, the second groove surface 34, and the fifth groove surface 48 that intersect at one point to form a cube edge vertex 62. Is formed by. Likewise, the sixth groove surface 50 lies in a plane substantially perpendicular to the third groove surface 40 and the fourth groove surface 42. In addition, when forming the sixth groove surface 50, a plurality of cuboid edge elements 70a, 70b, etc. (collectively denoted by reference numeral 70) are generated on the machined surface 16 of the thin plate 10. Each cube edge element 70 is a portion of the third groove surface 40, the fourth groove surface 42, and the sixth groove surface 50 intersecting with each other at one point to form a cube edge vertex 72. Is formed by. Preferably, both fifth groove surface 48 and sixth groove surface 50 form a plurality of cube edge elements on the machining surface 16 of the thin plate 10. However, the third groove 46 may optionally be formed such that only the fifth groove surface 48 or the sixth groove surface 50 forms a cube edge element.

The three mutually perpendicular optical surfaces 32, 40, 48 and the optical surfaces 34, 42, 50 of each cube edge element 60, 70 are each preferably formed in a single sheet. All three optical surfaces are preferably formed by a machining process to ensure a surface of optical quality level. In order to minimize alignment problems and damage in thin plate handling, it is desirable to maintain flat interfaces 12 and 14 between adjacent thin plates during the machining step and subsequent steps.

In a preferred method, the plurality of thin plates 10 are reoriented so that each first reference plane 24 lies approximately parallel to the reference axis 82 before the plurality of grooves 46 are formed. However, the grooves 46 may each be formed in a thin plate oriented such that its first reference plane is angled with respect to the reference axis 82. In particular, in some embodiments, it may be desirable to form each third groove 46 in each thin plate 10 lying at an angle β ₂ to exclude additional alignment steps in the manufacturing process. Preferably, the grooves 46 are also formed by high precision machining operations. In the disclosed embodiment, the diamond cutting tool having a 55.6 ° angle is moved along the axis across the machining surface 16 of each thin plate 10, which axis is substantially in the reference plane 24 of the thin plate 10. It is provided and parallel to the base surface 80. The grooves 46 preferably have their respective groove vertices 52 formed slightly deeper than the groove vertices of the first and second groove sets. Upon formation of the groove 46 a plurality of thin plates 10 having a surface of a structure substantially as shown in FIG. 12 is produced.

The machining surface 16 exhibits various necessary features as the retroreflective surface. The geometric shape of the cube edge element formed on the machined surface 16 of the thin plate 10 represents the geometry of the “complete” or “high efficiency” cube edge element because the geometry exhibits the most effective holes close to 100%. It is characterized by having. Thus, the retroreflective surface formed as a replica of the processing surface 16 exhibits high optical efficiency in response to light incident on the retroreflective surface along the axis of symmetry of the cuboid edge element. In addition, the cubic edge elements 60, 70 lie in opposite orientations and are symmetrical with respect to the first reference plane 24 and symmetrical retroreflective performance in response to light incident on the retroreflective surface at a large introduction angle. Indicates. However, the cube edge elements need not be symmetric about the reference plane.

In the embodiment shown in FIGS. 1-12 and 16-24, the thin plate is formed by keeping the spacing and depth of its grooves and the angle of the tool making the machined surface constant, so that the cube corner elements are substantially the same. Do. However, these factors can be altered to produce machined surfaces that differ in size, shape and orientation of the cube edge elements. 13-15 illustrate thin plates of exemplary variations fabricated within the scope of the present disclosure.

Fig. 13 shows cubic corner elements 160a, 160b, 160c, etc. (collectively denoted by 160) in a predetermined row lying in the first direction, and cube corner elements 170a, 170b, 170c, etc. in a predetermined row lying in the second direction. ), A thin plate 110 is shown. The thin plate 110 of FIG. 13 is characterized in that the various groove sets are formed at an angle other than the direction perpendicular to the reference plane 24 when viewed in plan. The thin plates 110, as described above, individually or as part of the assembly, cross each other at right angles to the second reference plane 26 with each reference edge intersecting the third reference plane 28 at an oblique angle φ ₁ . It can be formed by forming the first groove and the second groove so as to lie in the plane. Similarly, the third groove is formed along an axis crossing the first reference plane 24 at an oblique angle φ ₁ . In addition, the cube edge element 160 is not aligned with the cube edge element 170 on the sheet 10. The thin plate 110 includes a plurality of cube edge elements with holes varying in size and shape. Such changes in size and shape of the holes may be desirable to achieve certain optical objectives, such as, for example, to increase the uniformity of the retroreflective pattern of the retroreflective article formed as a replica of the thin plate 110.

FIG. 14 shows a thin plate 210 formed along an axis 216 where the third groove 246 is parallel to the first reference plane 24 but displaced from the reference plane. In addition, since the angle θ ₁ and the angle θ ₂ are different from each other, the axis of symmetry of each opposing cube edge element 214, 216 is inclined at a different angle with respect to the second reference plane 26.

15 shows a first set of grooves formed by a tool with varying angles to create a surface of a structure having a plurality of cube edge elements 312a, 312b, 312c, 312d, 312e, 312f with varying sizes and angles; And / or the grooves A ₁ , A ₂ , A ₃ , A ₄ , A ₅ of the second set of grooves are shown. For example, the angles of the grooves A ₁ , A ₄ , A ₅ may be 90 °, while the angle of the grooves A ₂ may be 105 ° and the angle of the grooves A ₃ may be 75 °. . In addition, each peak and vertex of the cube edge element 312 lies at a variable distance from the bottom surface 318 of the thin plate 310.

By the method described above, the geometric shape of the cube edges can be produced in various ranges. The size, orientation and inclination angle of the cube edge element formed on the surfaces of the plurality of thin plates can be changed. The article can be made as a replica of a thin sheet. The foregoing discloses a plurality of embodiments of the geometry of the cube edges. The following paragraphs generally describe the angular relationship between the surfaces of the cube edge elements so that those skilled in the art can produce various geometric shapes of the various cube edge elements.

25-27 are top and side elevation views of the machined surface of the thin plate 410 on which a pair of opposing cube edge elements 460, 470 are formed. The thin plate 410 is characterized in that it is placed in the three-dimensional space by the reference planes (424, 426, 428) as described above. For illustration purposes, the cube edge element 460 can be formed as a unit cube with three substantially mutual optical surfaces 432, 434, and 448. Optical surfaces 432 and 434 are formed by opposing surfaces of parallel grooves 430a and 430b that intersect along reference edge 436. The optical surface 448 is formed by one surface of the groove 446. The grooves 430a and 430b have respective vertex portions 433a and 433b extending along an axis crossing the third reference plane at any angle φ. Likewise, the groove 446 extends along an axis crossing the first reference plane at any angle φ. The angle φ is the angle of rotation of the cube edge element on the surface of the sheet. Depending on the machining constraints, the range of angles φ may vary from 0 ° to almost 90 ° such that the groove set is formed along an axis substantially coincident with the reference planes 424, 428. However, it is preferable that angle (phi) is 0 degrees-45 degrees.

FIG. 26 is a side elevational view of unit cube 460 taken along lines 26-26. The reference plane 456 coincides with the vertex of the groove 446 and lies in a direction perpendicular to the second reference plane 426. The angle α ₁ forms an acute angle between the cube surface 448 and the reference plane 456. Groove vertices 433a and 433b lie at an acute angle θ with respect to the second reference plane 426. FIG. 27 is a side elevational view of the unit cube 460 taken along lines 27-27. Reference planes 450a and 450b coincide with vertices 433a and 433b, respectively. The angle α ₂ forms an acute angle between the cube surface 432 and the reference plane 450a. Likewise, angle α ₃ forms an acute angle between the cube surface 434 and the reference plane 450b.

The second Cartesian coordinate system may be set using the groove vertex as a reference axis forming the unit cube 460. In particular, the x-axis may be set parallel to the intersection of the reference plane 456 and the second reference plane 426, the y-axis being the intersection of the reference plane 450b and the second reference plane 426. It can be set parallel to the line, and the z-axis extends in a direction perpendicular to the second reference plane 426. By adopting this coordinate system, standard unit vectors N ₁ , N ₂ , N ₃ can be formed for each unit cube surface 448, 432, 434 as follows.

Surfaces 432, 434, 448 should lie in substantially mutually perpendicular directions. Therefore, the dot product of the standard vector is zero.

N _{1 ·} N ₂ = N _{2 ·} N ₃ = N _{1 ·} N ₃ = 0

Thus, the following conditions are maintained.

α ₁ = θ

The set of angles α ₁ , α ₂ , α ₃ , θ corresponds to this condition forming a retroreflective cube edge element. In practice, the manufacture of thin plates with retroreflective cube edges can select an angle α ₁ value to orient the optical axis of the cubic edge element at a desired angle with respect to the base face of the retroreflective thin plate formed as a replica of the mold. As noted above, this specification is intended to be of little deviation from a perfect right angle designed to alter the pattern characteristics of the retroreflected light.

Sheet metal is dimensioned to maintain precise tolerances, such as machined plastics (e.g. polyethylene terephthalate, polymethyl methacrylate, polycarbonate) or metals (e.g. brass, nickel, copper or aluminum). It may be formed of a material having stability. The physical dimensions of the sheet are mainly limited by the machining constraints. The thin plate preferably has a thickness of at least 0.1 mm, a height of 5.0 to 100.0 mm, and a width of 10 to 500 mm. These measurements are provided for illustration only and are not intended to be limiting.

In the manufacture of retroreflective articles, such as retroreflective thin plates, the structural surfaces of the plurality of thin plates are used as master molds that can be replicated using electroforming or other conventional replication techniques. The plurality of thin plates may comprise substantially the same cuboid edge elements, or may comprise cuboid edge elements of varying size, geometry, or orientation. The structural surface of the replica, referred to in the art as a "stamper", has a negative image of the cuboid edge element. This copy can be used as a mold to form the retroreflective surface. More typically, however, a plurality of embossed or intaglio copies are combined to form a mold that is quite useful for forming retroreflective laminates. Retroreflective thin plates can also be produced, for example, by embossing the preformed thin plates with a row of cube edge elements as described above or by molding a fluid material in the mold. Optionally, the retroreflective sheeting may be molded by contacting a cube edge element with a preformed film as taught in PCT Application WO 95/11464 and US Pat. No. 3,648,348, or preformed with a preformed cube edge element. It can be prepared as a layered article by laminating the shaped films. By way of example, such a thin plate can be manufactured using a nickel mold formed by electroplating nickel on a master mold. The electroforming mold is used as a stamper for embossing a mold pattern on a polycarbonate film having a refractive index of about 1.59 and a thickness of approximately 500 mu m. The mold may be used in a press where the compression is performed at a temperature of approximately 175 to 200 ° C.

Materials useful for the production of such reflective thin plates are those having dimensional stability, durability, which are not affected by weather, and which can be molded quickly into a desired shape. Examples of suitable materials include acrylics, which generally have a refractive index of about 1.5, such as Plexiglas resin from Rohm and Haas; Thermoplastic acrylates and epoxy acrylates having a refractive index of about 1.6, preferably radiation cured polycarbonates; Polyethylene-based ionomers (commercially available under the trade name "SURLYN"); Polyester; And cellulose acetate butyrate. Materials that are moldable under ordinary heat and pressure and that are generally optically transmissive may be used. Other materials suitable for forming retroreflective thin plates are disclosed in US Pat. No. 5,450,235 to Smith et al. The thin plates may also contain colorants, dyes, UV absorbers, or other necessary additives.

In some circumstances it is desirable to provide a backing layer in the retroreflective sheeting. The backing layer is particularly useful for retroreflective laminates that reflect light according to the principle of total internal reflection. Suitable backing layers can be effectively combined with the disclosed retroreflective thin plates and can be made of transparent or opaque materials containing coloring materials. Suitable backing materials include aluminum sheets, galvanized steel, polymethyl methacrylates, polyesters, polyamides, polyvinyl fluorides, polycarbonates, polymeric materials such as polyvinyl chloride, polyurethane, and these and other materials. There are various laminates that are made with.

The backing layer or sheet may be sealed in a grid or any other shape suitable for the reflective element. Sealing may be accomplished using various methods, including ultrasonic welding, adhesives, or by heat sealing at separate locations in the row of reflective elements (see US Pat. No. 3,924,928). Sealing is desirable to prevent the ingress of contaminants such as soil and / or moisture, and is also desirable to preserve air in the space adjacent to the reflective surface of the cube edge element.

If the composite needs to be strengthened in strength or toughness, a backing sheet of polycarbonate, polybutyrate or fiber reinforced plastic can be used. Depending on the degree of flexibility of the retroreflective material so formed, the material may be rolled up or cut into strips or other suitable structures. The retroreflective material may also be backed with adhesive and release sheet, such that the retroreflective material may be attached to the substrate without the additional step of attaching the adhesive or using other fastening means.

The cube corner elements disclosed herein can be individually tailored such that light retroreflected by the article is dispersed in a desired pattern or divergence profile, as taught in US Pat. No. 4,775,219. Typically, half-angle errors of grooves are less than ± 20 arc minute, often less than ± 5 arc minute.

Example

Approximately 25 thin plates, 127.0 mm in length, 25.4 mm in height, and 0.508 mm in thickness, were assembled into a fixture substantially as shown in FIG. 16. The thin plates were formed of 70/30 brass, and the first and second major surfaces of the plurality of thin plates were polished to have a surface roughness of approximately 0.005 to 0.025 microns. A wedge block having a precisely formed inclined surface is held in the assembly at a fixed position in which the inclined surface lies at an angle of 27.8 ° from the vertical reference axis to the base surface of the fixture, so that each first reference plane of the plurality of thin plates The angle was set at an angle of 27.8 ° from the axis. The first set of grooves were formed by moving a diamond machining tool across a plurality of thin plates along an axis substantially perpendicular to the major surface of the thin plates. The grooves were formed uniformly to a depth of approximately 0.154 mm and the groove vertices were spaced at a distance of approximately 0.308 mm.

Thereafter, the plurality of thin plates was separated from the fixture and placed so that the first reference planes of the plurality of thin plates were placed at an angle of 27.8 ° from the reference axis. A second set of grooves was formed by moving a diamond machining tool across a plurality of thin plates along an axis substantially perpendicular to the major surface of the thin plates. The grooves were formed uniformly to a depth of approximately 0.154 mm and the groove vertices were spaced at a distance of approximately 0.308 mm. The grooves were also formed along an axis substantially coplanar with the axis of the corresponding groove of the first set of grooves.

The plurality of thin plates was separated from the fixture and rearranged such that the first reference plane of each thin plate was substantially perpendicular to the base surface of the fixture. A third set of grooves was then formed by moving the diamond machining tool at an inclination angle of 55.6 ° along an axis substantially coincident with the first reference plane of each thin plate of the assembly. This machining step resulted in a machining surface having an embossed image of a row of optically opposed cube edge elements as substantially shown in FIG. 24.

The thin plates were then removed from the assembly, washed and reassembled in the fixture to form a master tool. Nickel stamper tools were formed from the surface of the master tool using chemical vapor deposition of nickel. The reflection coefficient of the nickel surface, such as a mirror for dazzling light, is about 0.62 to about 0.64. The nickel stamper was arranged at an orientation angle of about 0 ° and an introduction angle of about -4 ° and the light return rate was measured for this. The light recovery rate data was adjusted to match a circular area of about 26.99 mm (1.0625 inch) in diameter. The light return increments and cumulative rates for various observation angles are shown in Table 1 below.

Incremental Observation Angle Increment Cumulative rate 0-0.1 4.764 4.76 0.1-0.2 8.438 13.20 0.2-0.3 3.500 16.70 0.3-0.4 0.639 17.34 0.4-0.5 0.592 17.93 0.5-0.6 0.359 18.29 0.6-0.7 0.259 18.55 0.7-0.8 0.209 18.76 0.8-0.9 0.181 18.9 0.9-1.0 0.167 19.1

For comparison, it is used to produce a retroreflective sheet with a truncated conical cuboid corner element with a basic triangle angle of about 70 ° -55 ° -55 ° according to Hoopman's US Pat. No. 4,588,258. The light recovery rate for the nickel stamper tool was measured. The stamper tool was positioned such that its orientation angle was about 180 ° and the introduction angle was about −4 °. The light recovery rate data is for a circular area about 26.99 mm (1.0625 inch) in diameter. The light return increments and cumulative rates for various observation angles are shown in Table 2 below.

Incremental Observation Angle Increment Cumulative rate 0-0.1 1.369 1.369 0.1-0.2 3.115 4.484 0.2-0.3 3.197 7.681 0.3-0.4 0.938 8.618 0.4-0.5 0.911 9.530 0.5-0.6 0.434 9.964 0.6-0.7 0.229 10.193 0.7-0.8 0.143 10.335 0.8-0.9 0.103 10.439 0.9-1.0 0.078 10.517

The present invention has been described with reference to the plurality of embodiments so far. Those skilled in the art will be able to make various changes in the described embodiments without departing from the scope of the invention. Thus, the scope of the present invention should not be limited by the preferred structures and methods described herein, but by the broad scope of the claims below.

Claims (44)

A thin plate suitable for use in a mold for forming a retroreflective article having a cuboid edge, comprising: opposing first and second major surfaces defining a first reference plane therebetween; Also having a machining surface connecting between the second major surfaces, the machining surface having a second reference plane that is substantially parallel to and perpendicular to the first reference plane, the first reference surface and the second reference plane In the thin plate defining a third reference plane perpendicular to the Two parallelly contiguous V-shaped grooves having a first groove surface and a second groove surface that form a first reference edge that is substantially orthogonal and inclined at a first angle with respect to the second reference plane to the machined surface of the thin plate. A first groove set including at least; Parallel to the processed surface of the thin plate, having a third groove surface and a fourth groove surface that are substantially perpendicular to the second reference plane and form a second reference edge that is inclined at a second angle different from the first angle. A second groove set comprising two or more adjacent V-shaped grooves; And At least one first, having a fifth groove surface and a sixth groove surface, wherein the fifth groove surface is disposed in a first direction substantially perpendicular to the first groove surface and the second groove surface; Forming a cube edge, wherein the sixth groove surface is substantially orthogonal to the third groove surface and the fourth groove surface to form at least one second cube edge disposed in a second direction different from the first direction. A third groove set comprising one or more such grooves A thin plate comprising a. A thin plate suitable for use in an article molding mold having a retroreflective cuboid edge, comprising: an opposing first and second major surfaces defining a first reference plane therebetween, Also provided with a machining surface connecting between the second major surfaces, the machining surface having a second reference plane that is substantially parallel to and perpendicular to the first reference plane, the first reference plane and the second reference plane In the thin plate defining a third reference plane perpendicular to the A first set of grooves comprising, on a processing surface of the thin plate, two or more parallel contiguous V-shaped grooves having a first groove surface and a second groove surface that are substantially orthogonal to form a first reference edge; A second groove set including at least two parallel grooved V-shaped grooves having a third groove surface and a fourth groove surface that are substantially orthogonal to form a second reference edge on the processed surface of the thin plate; And At least one agent disposed in the first direction on the processing surface of the thin plate, having a fifth groove surface and a sixth groove surface, the fifth groove surface being substantially orthogonal to the first groove surface and the second groove surface; Form a first cube edge, wherein the sixth groove surface is substantially orthogonal to the third groove surface and the fourth groove surface, so that at least one second cube edge disposed in a second direction different from the first direction. A third groove set comprising one or more such grooves to form And at least one cube edge comprises a plurality of non-identical cube edge elements. The thin plate according to claim 2, wherein at least one of the first groove set and the second groove set includes grooves having different depths in the processing surface of the thin plate. The thin plate according to claim 2, wherein the fifth groove surface and the sixth groove surface cross each other to form groove vertices extending along an axis crossing at a right angle with the first reference plane. The thin plate according to claim 1 or 2, wherein the first groove surface and the second groove surface are inclined at different angles with respect to an axis perpendicular to the second reference plane. The thin plate according to claim 1 or 2, wherein at least one of the first set of grooves and the second set of grooves includes grooves having different included angles. 3. A thin plate according to claim 1 or 2, wherein the first and second groove sets comprise a plurality of grooves, each of which has an angle between about 10 degrees and about 170 degrees. 8. The thin plate of claim 7, wherein the distance between the first set of grooves and the adjacent reference edge of the second set of grooves is from about 10 microns to about 1000 microns. 3. A thin sheet according to claim 1 or 2, wherein the third set of grooves consists essentially of a single groove. 10. The thin plate of claim 9, wherein the single groove extends along an axis substantially parallel to the first reference plane. The thin plate according to claim 1 or 2, wherein the first major surface and the second major surface are substantially planar. A mold assembly comprising a plurality of thin plates according to claim 1 or 2. 13. The mold assembly of claim 12, wherein each sheet is about 0.025 to 5 mm thick. Retroreflective sheet made of a mold according to claim 13. A thin plate suitable for use in a mold for forming a retroreflective article having a cuboid edge, comprising: opposing first and second major surfaces defining a first reference plane therebetween; Also provided with a machining surface connecting between the second major surfaces, the machining surface having a second reference plane that is substantially parallel to and perpendicular to the first reference plane, the first reference plane and the second reference plane In the method for producing such a thin plate defining a third reference plane perpendicular to the Using the thin plate, in the first direction a first set of grooves comprising at least two parallel adjacent V-shaped grooves having a first groove surface and a second groove surface that are substantially orthogonal to form a first reference edge; Forming on the processed surface of the thin sheet; The second set of grooves, in the second direction, using the thin plate comprises at least two parallel adjacent V-shaped grooves having a third groove surface and a fourth groove surface that are substantially orthogonal to form a second reference edge. Forming on the processed surface of the thin sheet; And At least one agent disposed in the first direction, using the thin plate, having a fifth groove surface and a sixth groove surface, the fifth groove surface being substantially orthogonal to the first groove surface and the second groove surface. Form a first cube edge, wherein the sixth groove surface is substantially orthogonal to the third groove surface and the fourth groove surface, so that at least one second cube edge disposed in a second direction different from the first direction. Forming a third groove set including one or more such grooves provided on the processed surface of the thin plate in a third direction different from the first direction or the second direction; Thin plate manufacturing method comprising a. 16. The method of claim 15, wherein at least one of forming the groove sets comprises moving the sheet with respect to a fixed machining tool. 16. A method according to claim 15, wherein at least one of the steps of forming the groove set comprises holding the thin plate fixed and moving the machining tool relative to the thin plate. 16. The method of claim 15, wherein at least one of forming the groove sets comprises forming grooves of different depths in the processing surface. 16. The method of claim 15, wherein forming a first set of grooves comprises forming a groove such that the first reference edge is inclined at a first angle with respect to the second reference plane, thereby forming the second set of grooves. And forming a groove such that the second reference edge is inclined at a second angle different from the first angle with respect to the second reference plane. A thin sheet produced by the method according to claim 15. Retroreflective sheet made from a thin plate according to claim 20. A thin plate suitable for use in a mold for forming a retroreflective article having a cuboid edge, comprising: opposing first and second major surfaces defining a first reference plane therebetween; Also provided with a machining surface connecting between the second major surfaces, the machining surface having a second reference plane that is substantially parallel to and perpendicular to the first reference plane, the first reference plane and the second reference plane In the thin plate manufacturing method which manufactures several sheets of such thin plates which define the 3rd reference plane orthogonal to Orienting the plurality of thin plates such that their respective first reference planes are parallel to each other and also take a first angle with respect to a fixed reference axis; A first set of grooves is formed on the machined surface of each thin plate that comprises at least two substantially adjacent parallel V-grooves having a first groove surface and a second groove surface that are substantially orthogonal to form respective respective first reference edges on each thin plate. Doing; Orienting the plurality of thin plates such that their respective first reference planes are parallel to each other and disposed at a second angle with respect to the fixed reference axis; A second set of grooves is formed on the machined surface of each thin plate that includes at least two parallel adjacent V-shaped grooves having a third groove surface and a fourth groove surface that are substantially orthogonal to form respective second reference edges on each thin plate. Doing; Orienting the plurality of thin plates such that their respective first reference planes are parallel to each other and disposed at a third angle with respect to the fixed reference axis; And A fifth groove surface and a sixth groove surface, the fifth groove surface being substantially orthogonal to the first groove surface and the second groove surface, forming one or more first cube edges disposed in a first direction; And the sixth groove surface comprises one such groove defining substantially one or more second cube edges arranged in a second direction different from the first direction substantially perpendicular to the third groove surface and the fourth groove surface. Forming the third groove set including the above on the processed surface of the plurality of thin plates Thin plate manufacturing method comprising a. 23. The method of claim 22 wherein the step of orienting the plurality of sheet metals so that their respective first reference planes are parallel to each other and disposed at a first angle with respect to the fixed reference axis comprises assembling the plurality of sheet metals to an appropriate fixture. To include, The fastener is a thin plate manufacturing method characterized in that to form a base surface. 23. The method of claim 22, wherein the first and second angles are between about 1 degrees and about 85 degrees. 25. The method of claim 24, wherein the first angle is different from the second angle. 25. The method of claim 24, wherein the first angle is substantially the same as the second angle. 23. The method of claim 22, wherein forming the groove set comprises removing, using a material removal technique, a portion proximate to the processing surface of each of the plurality of sheet metals. 28. The method of claim 27, wherein the forming of the groove set comprises causing relative motion between the plurality of sheets and the cutting tool. 24. The method of claim 23, wherein at least one of the steps of forming the groove set includes causing relative motion to cause the cutting tool to move parallel to the base surface formed by the fixture. 24. The method of claim 23, wherein at least one of the steps of forming the groove set includes causing relative motion to cause the plurality of sheets to move parallel to the base surface formed by the fixture. Way. 23. The method of claim 22, wherein at least one of the steps of forming the groove set comprises forming grooves of different depths in the processing surface of the sheet. 23. The method of claim 22, wherein at least one of the steps of forming the groove set comprises forming grooves at non-uniform groove intervals on the processing surface of the sheet. 23. The method of claim 22, wherein at least one of the steps of forming the groove set comprises a ruling operation. 23. The method of claim 22, wherein at least one step of forming the groove set comprises a fly cutting operation. 23. The method of claim 22, wherein at least one of the steps of forming the groove set comprises a grinding operation. 23. The method of claim 22, wherein at least one of the steps of forming the groove set comprises a milling operation. 23. The method of claim 22, wherein the step of directing the plurality of thin plates such that their respective first reference planes are parallel to each other and takes a second angle with respect to the fixed reference axis comprises assembling the plurality of thin plates to a suitable fixture. Thin plate manufacturing method comprising the. 23. The method of claim 22, wherein forming the third set of grooves comprises forming each groove of the third set of grooves such that the fifth and sixth groove surfaces intersect along an axis orthogonal to the first reference plane orthogonally. Thin plate manufacturing method comprising a. 23. The method according to claim 22, wherein at least one of the first cube edge and the second cube edge is essentially disposed on one of the plurality of thin plates, respectively. 23. The method of claim 22, wherein the adjacent first and second major surfaces comprise a substantially planar interface. A plurality of thin sheets produced according to the method of claim 22. 23. The method of claim 22, further comprising replicating the processing surface of the plurality of sheet metals into an integral substrate to form a negative copy of the plurality of cube edge elements suitable for use in a mold for forming a retroreflective article. Thin plate manufacturing method comprising the. A mold made according to the method of claim 42. A retroreflective sheet made of the mold of claim 43.